Update index.md

Author: prigiattiperrut

src/connections/destinations/catalog/google-tag-manager/index.md

@@ -84,10 +84,21 @@ If you are seeing `404` error on the JavaScript console of your page and it is a
 
 
 ### Duplicate Events
+
 If you have Google Ads enabled and see duplicate events in GTM, check to see if the event is set as a conversion in Google Ads. Duplicate conversions are common when you use both Google Ads and GTM, since Segment's Adwords destination initializes the gtag script with the dataLayer itself. So, when you fire a mapped event, Segment submits the payload directly to the dataLayer.
 
 Google recommends using [transactionIds](https://support.google.com/google-ads/answer/6386790){:target="_blank"} to prevent this duplication. 
 
+### Duplicate Events triggering GTM tags multiple times
+
+In reviewing the "dataLayer" tab for each event in GTM, it was observed that the `eventModel` field, which is an internal Google field, is only present in events captured by the Google Ads SDK. To prevent GTM tags from firing multiple times due to duplicate events, you can create a GTM variable and use `eventModel` as a condition to filter events.
+
+1. Create a [GTM variable](https://support.google.com/tagmanager/answer/7683056?hl=en){:target="_blank"} to capture the `eventModel` field when events hit the Google DataLayer
+2. Set the variable to add the value "GTM" to the `eventModel` field when the field is not present in the event dataLayer. The format value should be set to "Convert undefined to GTM"
+3. Add the newly created variable to your GTM trigger so that only events containing `eventModel = GTM will` trigger the tag.
+
+This solution has been shared by other customers. Please test it before implementing it with production data. If you have any questions regarding the GTM setup, consult the [GTM documentation](https://support.google.com/tagmanager/answer/6103657?hl=en){:target="_blank"}.
+
 
 ## Appendices